Nonthymoma early-onset- and late-onset-generalized myasthenia gravis--a retrospective hospital-based study

Clin Neurol Neurosurg. 2007 Oct;109(8):686-91. doi: 10.1016/j.clineuro.2007.05.023. Epub 2007 Jul 17.

Abstract

Objective: Acquired myasthenia gravis (MG) is predominantly due to nicotinic acetylcholine receptor (AChR) autoantibodies (Ab). Differences between nonthymoma early-onset and late-onset MG were reported. We studied the clinical and serological characteristics of nonthymoma AChR Ab-positive-generalized MG patients.

Patients and methods: Chinese AChR Ab-positive-generalized MG patients who had generalized disease for 3 years or longer were studied.

Results: Among 41 such patients, 25 (61%) were female. The mean onset age was 43.5 years (range 9-78 years) and the mean follow-up duration was 7.8 years (range 3-20 years). Sixteen (39%) patients had late-onset disease (onset age >or=50 years). Compared to early-onset patients (onset age <50 years), late-onset patients were characterized by male predominance (p=0.002), absence of thymic lymphofollicular hyperplasia (p=0.036), and a higher striated muscle Ab seropositivity rate (94% versus 4%, p<0.001). Although there was no statistically significant difference in clinical severity and outcome or response to treatment between late-onset and early-onset patients, 50% and 75% of late-onset patients had moderate or severe disease at onset and worst status, respectively, compared to 28% and 52% for early-onset patients at onset and worst status, respectively. Also 63% of late-onset patients had disease progressed within first 3 years compared to only 40% of early-onset patients did.

Conclusion: Nonthymoma late-onset-generalized MG patients were common among Hong Kong Chinese, with a statistically non-significant trend that it was clinically more severe than early-onset MG but with similar clinical outcome or response to treatment; >90% of these patients were seropositive for striated muscle Ab.

MeSH terms

  • Adolescent
  • Adult
  • Age of Onset
  • Asian People / statistics & numerical data*
  • Autoantibodies / blood
  • Child
  • Child, Preschool
  • Female
  • Hong Kong / epidemiology
  • Humans
  • Male
  • Motor Endplate / metabolism
  • Muscle, Skeletal / metabolism
  • Myasthenia Gravis / diagnosis
  • Myasthenia Gravis / epidemiology*
  • Myasthenia Gravis / therapy
  • Receptors, Nicotinic / immunology
  • Retrospective Studies
  • Severity of Illness Index

Substances

  • Autoantibodies
  • Receptors, Nicotinic